Bedrock Dewatering for Construction of Marmet and Soo Lock Projects
Michael Nield Engineering Geologist Dam Safety Production Center, Huntington, WV August 2012
US Army Corps of Engineers
BUILDING STRONG® BEDROCK DEWATERING FOR CONSTRUCTION OUTLINE
1. Marmet Lock Replacement Project (construction) - Project Description - Site Geology - Permeability and Groundwater Inflow - Dewatering Provisions
2. Soo Lock Replacement Project (design) - Project Description - Site Geology - Permeability and Predicted Groundwater Inflow - Impact to Design
BUILDING STRONG® MARMET LOCK - PROJECT DESCRIPTION
. Located on Kanawha River, OHIIO RIVER near Charleston, West GREAT LAKES DIVISION Virginia.
. Permits economic river transportation of coal, MARMET aggregate and chemicals. LOCKS & DAM
. Construction of the new replacement lock was completed in 2009
BUILDING STRONG® “Busiest Lock in USA” Prior to New Lock
Twin 56’ X 360’ Chambers Completed in 1934
Aerial View – Original Locks
BUILDING STRONG® New 110’ X 800’ Lock Chamber
Original Locks
New Guard Wall
New Guide Walls
Aerial View – New Replacement Lock
BUILDING STRONG® MARMET LOCK - SITE GEOLOGY
. 157 TOTAL BORINGS . 10,200’ TOTAL DRILLING . 3,700’ ROCK CORE . 294 PRESSURE TESTS
Subsurface Exploration – Boring Location Plan
BUILDING STRONG® General Geology
. Soil thickness 40 to 60 feet
. Relatively flat top of rock surface at elev. 552 ± 3’
. Sedimentary rock of the Pennsylvanian-aged Kanawha Formation Sandstone member (23 to 43 feet thick) Shale member (19 to 33 feet thick)
. Low angled bedding with 0o-10o dip to the Northwest
. Slightly fractured with occasional high angled joints (70o-90o)
BUILDING STRONG® Bedrock Units - Sandstone Member
. Light gray . Moderately hard to hard . Medium to fine grained . Average unconfined compressive strength 8,442 psi . Foundation for lock walls . Occasional thin coal seam or zone of carbonaceous stringers
BUILDING STRONG® Bedrock Units - Shale Member
. Gray to dark gray . Moderately hard to soft . Silty . Average unconfined compressive strength 6,678 psi
BUILDING STRONG® Geologic Cross Section - During Construction
Anchored Anchored Retaining Existing Wall Landwall 600 600
550 550
500 500
-100 0 100
SOIL SANDSTONE WEAK SEAMS SHALE
Geologic Cross Section – Chamber Monoliths
BUILDING STRONG® MARMET LOCK – BEDROCK PERMEABILITY Pressure Testing PRESSURE GAUGE WATER LINE WATER METER VALVE BORE HOLE
BLADDER
OPEN DISCONTINUITIES
BEDROCK
5’
BUILDING STRONG® Pressure Testing . Measure water flow while maintaining predetermined pressure, typically recorded in gal/min, CFM. . Values are often converted to Lugeons
OPEN DISCONTINUITIES
BEDROCK
BUILDING STRONG® Hydraulic Conductivity
. 294 individual pressure tests in 36 holes located within cofferdam.
. Convert pressure testing results to Hydraulic Conductivity value K using equation from USBR:
K = Q/2πLH loge(L/r) (Q=flow, L=length tested, H=pressure, r=hole radius)
. Convert pressure test data to Lugeon then convert to Hydraulic Conductivity K: K = Lu x 10-7 (1 Lugeon equals one liter per minute per meter hole at a pressure of 10 bars)
BUILDING STRONG® Hydraulic Conductivity – Groundwater Inflow
. Average permeability or Hydraulic Conductivity (K) value from pressure testing results at Marmet is 1.69X10-6 m/s (5.54x10-6 ft/s), which is typical for sandstone.
. Average Hydraulic Conductivity values in bedrock increased when overlying soil was removed during construction at both Marmet and Winfield projects.
. Hydraulic Conductivity, along with known hydraulic gradient and excavated surface area can be utilized to help develop preliminary estimate of groundwater inflow during construction (using Darcy’s law). . Calculated inflow from average K value is 520 gal/min and upper bound inflow value is 7,000 gal/min.
BUILDING STRONG® Permeability Comparison – Logarithmic Scale
10-3 SOIL DEWATERING DESIGN VALUE
10-4 MAXIMUM TEST VALUE 10-5
10-6 MEAN TEST VALUE 10-7 CALCULATED
10-8 RANGE PUBLISHED RANGE 10-9 HYDRAULIC CONDUCTIVITY K (M/S) MARMET MARMET WINFIELD SANDSTONE DODSON-STILSON PRESSURE TESTS PRESSURE TESTS TYPICAL (Brassington, 1988)
BUILDING STRONG® MARMET LOCK – DEWATERING PROVISIONS
. Accurately portray bedrock conditions in contract documents, alerting the contractor to potential dewatering concerns and work effort. Graphic Logs of Borings Geologic Sections Geologic Mapping Geotechnical Baseline Report
. Address in the specifications groundwater concerns during construction and provide appropriate bid items for compensation. Dewatering Grout Curtains Concrete Placement Anchor Installation
BUILDING STRONG® Graphic Logs of Borings – Indicators of Permeability . QUANTIFY DESCRIPTIVE TERMS IN LEGEND
. INCLUDE DOWN-HOLE CAMERA IMAGES IF TOP OF ROCK AVAILABLE AND DEPTH OF WEATHERING DRILL WATER LOSS
BEDDING PLANE SPACING
PRESSURE TEST DATA
FRACTURES
IRON STAINING RQD
SEAMS
BUILDING STRONG® Existing Foundation Maps – Indicators of Permeability
. Fracture orientation, spacing, length and aperture . Foundation grout takes . Records of groundwater seepage and control methods
EXCAVATION FOR NEW LOCK – IN THE DRY
28.5’ ORIGINAL CONCRETE LOCK WALL - COFFERDAM
56’ ORIGINAL LOCK CHAMBER – KANAWHA RIVER
Original Lock Chamber and Lock Wall
BUILDING STRONG® Existing Foundation Maps – Indicators of Permeability
. Fracture orientation, spacing, length and aperture . Foundation grout takes . Records of groundwater seepage and control methods
5” WIDE CREVICE FRACTURE LENGTH +70’ 1.2’ WIDE CREVICE 0.4’ WIDE 0.05’– 0.1’ WIDE OPEN 0.05’- 0.1’ WIDE
0.03’ WIDE OPEN 0.0’– 0.1’ WIDE 0.7’– 1.0’ WIDE 0.05’ WIDE
Original Lock Chamber and Lock Wall
BUILDING STRONG® Groundwater Flow Through Fractures
Fractures are the primary mechanism for bedrock groundwater inflow into an excavation.
Groundwater flow can be estimated through individual bedrock fractures utilizing the following equation (maximum value – does not take into consideration joint roughness, shape, infilling, laminar flow etc.):
γ µ 3 q = w/12 w e i (q=flow, γw=unit weight of water, µw=dynamic viscosity of water, e=fracture aperture, i=hydraulic gradient)
BUILDING STRONG® Cofferdam – Construction of New Lock – Aerial View
Cofferdam (sheet pile cells and original lock) Slurry Wall and Relief Wells
Soil Retaining Wall
New Lock Chamber
BUILDING STRONG® Cofferdam – Construction of New Lock – Rock Excavation
Original Lock Sheet Pile Cells Soil Retaining Wall
BUILDING STRONG® COFFERDAM: Barge Tow ORIGINAL LOCK
KANAWHA RIVER
553 Anchors
SANDSTONE NEW LOCK MEMBER FOUNDATION Hydraulic gradient ranges 531 from 0.13 to 1.2 523.2 Uplift pressures measured SHALE using piezometers during MEMBER construction – found to be as anticipated or less. Cofferdam – Hydraulic Gradient & Uplift
BUILDING STRONG® Specifications – Dewatering Bedrock Groundwater
. “The Dewatering Systems shall be designed and operated so as to allow construction of the lock chamber to be accomplished essentially in the dry, as well as to facilitate construction of all other project features.” . “The Contractor's Dewatering System shall be designed in order to control groundwater, surface water, and incidental water, including seepage through the rock foundation… . “…and then sumping the remaining groundwater and any other seepage into the bottom of the excavation.” . “…dewatering facilities and supplemental dewatering facilities that may be required to control any seepage from excavated slopes or into the bottom of the excavation...” . “Supplemental measures may include the installation of wellpoints, inverted filters, french drains, relief wells drilled into either soil or rock, and appropriate pumps, piping, and appurtenances as necessary…”
BUILDING STRONG® Control Groundwater Seepage – Concrete Placement
“Rock surfaces upon which concrete is to be placed shall be clean and free from oil, standing or running water, ice, mud, drummy rock, coatings, debris, and loose, semi-detached, overhanging, or unsound fragments.”
BUILDING STRONG® Control Groundwater Seepage – Foundation Treatment
Profile – Prior to Concrete Lift Placement
BUILDING STRONG® Control Groundwater Seepage – Foundation Treatment
Profile – After Concrete Lift Placement
BUILDING STRONG® Control Groundwater Seepage - Foundation
BUILDING STRONG® Isolate Groundwater Seepage from Mass Concrete Placement
BUILDING STRONG® Dewater and Control Groundwater Seepage
Primary Discharge Pump
Control of Seepage - Sidewalls
Sand Bags & Sump Pump
BUILDING STRONG® Provisions in Specifications Concerning Artesian Pressure
Control Artesian Pressures: . Grouting for Foundation Anchor Installation . Foundation Drilling and Grouting
BUILDING STRONG® Foundation Drilling and Grouting
. Grout Curtain Inhibits Groundwater Flow Into Lock Chamber . Grout Curtain Extends to Elevation 510 . 10’ Spacing Between Primary and Secondary Holes . Optional Tertiary and Higher Order Holes
BUILDING STRONG® Top of Rock Surface
Gravel Filter at Base of Retaining Wall
Know Location of Top of Rock Surface: . Sheet Pile Driven to Rock – Cofferdam & Retaining Wall . Seepage Cutoff Wall Through Soil – Key into Rock
BUILDING STRONG® BEDROCK DEWATERING FOR CONSTRUCTION OUTLINE
1. Marmet Lock Replacement Project (construction) - Project Description - Site Geology - Permeability and Groundwater Inflow - Dewatering Provisions
2. Soo Lock Replacement Project (design) - Project Description - Site Geology - Permeability and Predicted Groundwater Inflow - Impact to Design
BUILDING STRONG® SOO LOCKS – PROJECT DESCRIPTION
SOO LOCKS . Located in Michigan’s Upper OHIIO RIVER Peninsula at Sault Ste. Marie GREAT LAKES DIVISION and near Canadian boarder.
. All shipping in/out of Lake Superior travels through Soo Locks
. New lock is in plans and specifications phase. Partial cofferdam has been constructed and approach channel deepened.
BUILDING STRONG® ONTARIO ST. MARYS RIVER
HYDROPOWER UNITS LOCKS MICHIGAN FALLS OF THE ST. MARYS
COMPENSATING WORKS
Aerial View of Project - Taken From Upstream
BUILDING STRONG® N
Aerial View of Locks
BUILDING STRONG® N
Aerial View of Locks – Proposed New Lock
BUILDING STRONG® SOO LOCKS – SITE GEOLOGY
- 76 Borings - 6,036 Total Feet of Exploratory Drilling - 4,139 Feet of Coring - 24 Piezometers Subsurface Exploration – Boring Location Plan
BUILDING STRONG® Subsurface Exploration – Down Hole Testing
496 Pressure Tests
21 Borehole Jack Tests 1,000’ of Down-the-Hole Camera Images
BUILDING STRONG® General Geology
. Soil and rock fill – 0 to 35 feet thick . Natural top of rock dips downstream (1%) – altered by past excavations . Jacobsville Sandstone Formation (Cambrian Age) - interbedded sandstones Hard Sandstone Member Moderately Hard Sandstone Member Shaly & Weathered Sandstone Members . Thin, continuous seams of clay, claystone and shale within sandstone. . Bedding plane dip in a westerly direction at a 3 percent slope.
BUILDING STRONG® Bedrock Units – Hard Sandstone
HARD SANDSTONE MEMBER is typically light gray, light red or light purple with few light gray reduction spots, hard to very hard, fine to medium grained, occasionally cross bedded and medium to thick bedded.
12,400 psi Average Unconfined Compressive Strength
Increased number of high-angled joints
BUILDING STRONG® Bedrock Units – Moderately Hard Sandstone
MODERATELY HARD SANDSTONE MEMBER is typically red with few to numerous light gray reduction spots, moderately hard, fine to medium grained and thin to medium bedded.
9,900 psi Average Unconfined Compressive Strength
The predominant member sampled.
BUILDING STRONG® Bedrock Units – Weathered and Shaly Sandstone
WEATHERED SANDSTONE MEMBER is typically red with numerous light gray reduction spots, moderately hard, fine to medium grained, moderately weathered and thin bedded.
SHALY SANDSTONE MEMBER is typically red to dark red with light gray reduction spots, soft to moderately hard, fine grained and thin bedded
Increased number of weak / clay seams within these two members.
BUILDING STRONG® Bedrock Units – Weak Seams
WEAK / CLAY SEAMS are typically thin (ranging from 0.4-foot to 0.02-foot thick), laterally continuous and have a scattered vertical distribution (1-foot to 7-foot vertical spacing). These weak seams consist of: - Clay Seams - Clay Coated Bedding Planes - Zones of Severely Broken Rock - Claystone or claystone interlaminated with clay seams
BUILDING STRONG® Bedrock Fractures
The predominant joint set orientation has been measured to have a dominant direction of N 70o E, and a secondary direction of N 30o E. Joints are typically high-angled (70o to vertical) with a smooth and planar surface, occasionally displaying some discoloration of the bedrock, and aperture ranging from tight to open with occasional clay coating or filling. Few faults were noted during construction of Poe Lock. These were high angled with limited vertical extent.
BUILDING STRONG® Geologic Cross Section – Existing Lock Chambers
TOP OF GROUND 600 600 EXISTING EXISTING SABIN TOP OF ROCK DAVIS LOCK LOCK 550 550
500 500
-100 0 100 200 300
Soil and Rock Fill Moderately Hard Sandstone Member Hard Sandstone Member Weathered and Shaly Sandstone Members Continuous Weak/Clay Seams
BUILDING STRONG® Geologic Cross Section – New Lock Chamber
NEW CONCRETE 600 600 NEW LOCK
550 550
500 ROCK ANCHORS 500
-100 0 100 200 300
Soil and Rock Fill Moderately Hard Sandstone Member Hard Sandstone Member Weathered and Shaly Sandstone Members Continuous Weak/Clay Seams
BUILDING STRONG® SOO LOCKS – PERMEABILITY
SABIN LOCK DAVIS LOCK
PRESSURE TEST RESULTS
Cross Section – Pressure Testing – Downstream Cofferdam
BUILDING STRONG® SABIN LOCK DAVIS LOCK
PRESSURE TEST RESULTS
Cross Section – Pressure Testing – Upstream Cofferdam
BUILDING STRONG® Hydraulic Conductivity – Groundwater Inflow
. Hydraulic Conductivity or Permeability of the bedrock is determined from pressure test results.
. Average bedrock permeability at the Soo Lock Replacement Project located between top of rock surface and the excavated chamber elevation (533.6) is 5.4 x10-3 ft/min.
. Magnitude greater than Marmet L&D (3.3x10-4 ft/min) or Winfield L&D (6.9 x10-4 ft/min).
. Individual pressure tests resulted in localized permeability of 1.3x10-1 ft/min (comparable to clean sand) and flow rates up to 9.3 cfm (70 gal/min) within a 5-foot increment.
. Estimated groundwater inflow through bedrock ranged from 1,480 to 2,625 gpm.
BUILDING STRONG® Seepage Through Bedrock During Dewatering
BUILDING STRONG® Groundwater Inflow During Construction
. Study performed in 2010 by Dr. Frank Schwartz, Ohio State University. . Preliminary study with limited scope. . Developed groundwater model using FTWORK, a finite-difference modeling package.
Summary: Trial 1 dewater new lock excavation only, Trial 2 dewatered new lock and Davis Locks. Trial 3: same as 2 with conservative grout curtain, Trails 4&5: same as 3 with varying K values.
BUILDING STRONG® Groundwater Model
Map of Model Grid in Relation to the Lock Structure
BUILDING STRONG® Groundwater Model
Distribution of Hydraulic Head
BUILDING STRONG® SOO LOCKS – IMPACTS TO DESIGN Grout Curtain for Dewatering Purposes - Upstream
GROUT CURTAIN
NEW LOCK
Plan View – Upstream Monoliths
BUILDING STRONG® Grout Curtain and Slurry Trench for Dewatering Purposes Downstream
SLURRY TRENCH
NEW LOCK GROUT CURTAIN
Plan View – Downstream Monoliths
BUILDING STRONG® Grout Curtain Details
BUILDING STRONG® Groundwater Flow Into Excavation – Lock Chamber
EXISTING NORTH NEW SOUTH DAVIS LOCKWALL WALL SOIL
SKIRT WALL
EXCAVATED LOCK CHAMBER
NEW CULVERT
HYDROSTATIC BEDROCK PRESSURE
BUILDING STRONG® Groundwater Flow Into Excavation – Drainage Sheets
EXISTING NORTH DAVIS LOCKWALL SOIL
SKIRT WALL
DRAINAGE SHEETS (Required to reduce hydrostatic pressure against Skirt Wall)
HYDROSTATIC BEDROCK PRESSURE
BUILDING STRONG® Groundwater Flow Into Excavation – Drainage Sheet Details
BUILDING STRONG® BUILDING STRONG®